Method and apparatus for hatching crustacea

ABSTRACT

A tank apparatus and method for providing advantageous environment for the hatching and early development of crustacean larvae. A plurality of hatching chambers, each having an adjacent larval chamber, with a low bulkhead separating the larval chamber from the hatching chamber. Light sources near the larval chambers cause the larvae to migrate to the latter chambers when the water level is above the bulkhead and the screening is removed. A removable screen mesh can be mounted atop the bulkhead to contain the larvae in the larval chamber. A spray arrangement is also provided to wash down the walls forming the larval chamber portion of the hatching tank to prevent larvae from jumping out and air is supplied to the hatching tank.

United States Patent Day et al. 1 Oct. 10, 1972 [54] METHOD ANDAPPARATUS FOR 3,062,183 11/1962 Tate .L ..l19/15 HATCHING CRUSTACEA3,540,414 11/1970 Maloney,Jr. ..1 19/2 [72] Inventors: 1 E' fii gIgrschmn Primary Examiner-Aldrich F. Medbery o o o au er Attorney-Darby&Darby [73] Assignee: Ocean Protein Corporation, New

York, NY. ABSTRACT v 22 Filed; p s, 1970 A tank apparatus and method forproviding advantageous environment for the hatching and early PP 96,133development of crustacean larvae. A plurality of r hatching chambers,each having an adjacent larval Related Appllcauon Data chamber, with alow bulkhead separating the larval [63] Continuation-impart of Ser. No.887,814, Dec. chamber from the hatching chamber. Light sources 24 1969near the larval chambers cause the larvae to migrate to the latterchambers when the water level is above 52 US. Cl ..119/2, 1 19/5 thebulkhead and the Screening is removed. A removal- 51 Int. Cl. ..A01k61/00 ble Screen mesh can be mounted p the bulkhead to 58 Field ofSearch ..119/2 5 contain the larvae in the larval Chambfl A Sprayrangement is also provided to wash down the walls [56] References Citedforming the larval chamber portion of the hatching tank to preventlarvae from jumping out and air is sup- UNITED STATES PATENTS plied tothe hatching tank- 2,984,207 5/1961 Drake 1.] 19/2 15 Claims, 4 DrawingFigures PATENTEDUCI 101972 3.696, 788

SHEET 1 0F 2 INVENTORS om/ .Dw

B904 6. hex/ MN PATENTEDnm 10 1912 3, 696. 788

sum 2 or 2 INVENTORS JOHN J. DAY

B PAUL S. HIRSCHMAN ATTORNEYS METHOD AND APPARATUS FOR HATCI-IING ICRUSTACEA RELATED APPLICATION This application is a continuation-in-partof our copending application Ser. No. 887,814, filed Dec. 24, 1969,entitled HATCl-IING TANK FOR CRUSTACEA, which is assigned to the sameassignee.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an apparatus and method for providing an optimum environmentfor the hatching and early development of crustacean larvae.

2. Description of the Prior Art The prior art relevant to the husbandryof crustaceans is generally primitive. A widely used practice is tosimply place large numbers of crustacea of similar age into a containedpond and allow them to grow, harvesting some crustaceans from time totime.

One of the problems with this practice is that crustaceans, especiallyshrimp, tend to be quite cannibalistic. This cannibalistic tendencybecomes evident at an early age. Shrimp larvae which hatch in thepresence of other larvae only a few days older are in danger of beingeaten by their elders, since the early development is quite rapid, and afew days additional age will enable a shrimp larvae to grow large enoughto eat newly hatched larvae.

Larvae often require water conditions different from those suitable foradult crustaceans. It has been found that in order to obtain optimumgrowth and survival rates of young shrimp or other crustaceans, it ishighly useful to exert precise control over water conditions. A singlehatching of shrimp can yield from 50,000 to 100,000 larvae. Theseimmense numbers of larvae can cause the water to be contaminated withwaste products and food. This contamination is deleterious to thedevelopment of the larvae. Also, precise temperature control over thewater is desirable. Furthermore, for certain species such as certainMacrobrachium carv cirrus species, it has been found desirable to hatchthe young shrimp in freshwater, and within a short time alter theirsurroundings to obtain a desired salinity. Experiments with the speciesMacrobrachium carcinus indicates that optimum salinity is between 12 and20 parts per thousand of salt in water.

As is obvious, it would be extremely difficult to exert this type ofwater control over an entire large pond, in order to promote the mostrapid and successful development of larvae. Furthermore, even if thiscould be done, it would probably not be desirable to the entire shrimpcommunity present in the pond to alter significantly the salinity of thewater.

In the raising of certain types of crustaceans under controlledconditions in tanks, it also has been found that at a certain point intheir development as larvae and prior to metamorphosis the larvae beginjumping. In some cases, the larvae can jump out of the tank and bekilled. J

OBJECTS OF THE INVENTION Another object of this invention is to enablefrequent treatment of the water environment of the larvae withoutdisturbing or damaging them.

A further object of the invention is to provide a hatching tank forcrustacea. I I

Still another object is to provide a tank for growing of crustaceanlarvae in which an arrangement is provided for preventing the larvaefrom jumping out of the tank.

' SUMMARY OF THE INVENTION This invention is an apparatus and method forproviding an optimum environment for the hatching and development ofshrimp or other crustacean larvae. The apparatus comprises a tankcontaining a number of hatching chambers separated from one another bysolid walls. Each hatching chamber has adjacent to it a larval chamber,the two chambers being separated by a bulkhead. Removable screen meshdividers are provided to be inserted at will atop the bulkheads. Lightsources are positioned near each of the larval chambers.

The shrimp are hatched in the hatching chambers, and the light sourcesturned on. This causes the shrimp larvae to migrate over the bulkhead ifthe water level is sufficiently high. Once inside the larval chambers,the screens are positioned to prevent re-entry into the hatchingchambers. With the larvae thus contained, operations can be performedupon the water in both chambers without danger of injuring the larvae.This is done by operating in the vacated hatching chamber.

To prevent the larvae from jumping out of the tank during their growthperiod, an arrangement is provided for washing down the side walls ofthe tank with water. This is done during the period of the growth cyclewhen the larvae have a tendency to jump out of the tank.

DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the hatchingtank of this invention, showing hatching and larval chambers, bulkheads,screen mesh, light sources and standpipes.

FIG. 2 is a side view of the hatching tank of this invention, takenpartially in cross section, showing the standpipe, drainpipe and valvearrangements for controlling the water environment within the tank.

FIG. 3 is a plan view of another hatching tank in accordance with theinvention in which the larvae are reared.

FIG. 4 is an elevational view, in cross-section, of the tank of FIG. 3.

DESCRIPTION OF THE INVENTION The basic component of the hatching tank istank body 10. Tank 10 can be, for example, approximately 20 feet long, 8feet wide and 3 feet in depth. Within tank body 10 are located a numberof adjacent hatching chambers 12, each separated from the others bysolid wall 14. Adjacent each hatching chamber l2'is a larval chamber 13.Each larval chamber is separated from its adjacent hatching chamber by alow bulkhead 15. Bulkhead 15 is about 2 feet high in the exemplary tankbeing described. Bulkhead 15 may be removable if desired but may bepermanently joined to the bottom of the tank body 10. v

Removable screen mesh dividers 18 are provided, one to each bulkhead,and are capable of being removably mounted vertically atop each ofbulkheads 15.- The larval chambers are separated from one another bysolid wall 16.

Standpipes 20, drainpipes 22 and valve 21 control overflow of water fromthe tanks. A hose 23 and pump 24 are also provided in order to enableinsertion or removal, of water fromthe tanks. To maintain the properwater temperature in the larval tanks, heaters can ,be immersed directlyinto the tanks or the water supplied to the tanks pre-heated. Air isalso supplied to each of the larval tanks through a pipe 29 which lieson the floor of each tank. This assures the larvae of an adequate supplyof oxygen.

In order to utilize'this invention, a female crustacean such as a shrimpof the species Macrobrachium carcinus, bearing fertilized eggs, isplaced in each hatching chamber 12. The water level of hatching chamber12 is below the levelof bulkhead 15 so that initially there is nocirculation of water between a larval chamber 13 and its associatedhatching chamber 12. The water in a hatching chamber 12 contains littleor no salt, while the water in a larval chamber can be kept at anydesired salinity.

Removable covers 25 are provided to cover hatching chambers 12. Thereason for this is that it is desirable for the female to remain quitecalm and quiescent during the hatching process. Darkness encouragescalm.

Sufficient salt is placed in each larval chamber 13 such that when thewater level in its associated hatching tank 12 is raised to its maximumdesirable level after hatching and thus spills over bulkhead 15, theentire volume of water in the unit comprising a hatching chamber 12 anda larval chamber 13 will contain salt in a desired ratio. This can be,for example, approximately 12 and parts per thousand by weight of saltto water.

During the hatching process, however, the water level is kept below thelevel of bulkhead 15 in a hatching chamber 12. When the shrimp larvaebegin to hatch, they can be seen with the naked eye when hatching tank12 is carefully examined. The hatching process itself takes only a fewhours, and from 50,000 to 100,000 larvae per hatch are obtained.

The female is preferably allowed to remain in her hatching chamber forfrom 24 to 48 hours after larvae are first observed. This assures thecompletion of hatching. The female is then removed from the hatchingchamber and returned either to a mating tank or to her normalenvironment. This leaves the larvae swimming alone in the hatchingchamber in a medium of fresh water.

At this point, pump 24 and hose 23 are utilized to fill the hatchingchamber 12 in which the larvae were just hatched to a level such thatthe water spills over bulkhead 15 into the adjacent larval chamber 13.The water is allowed to continue to rise until the maximum desirablewater level is reached with both the hatching chamber and its associatedlarval chamber filled, and the water level several inches above the topof bulkhead 15. The entry of water from hatching chamber 12 into larvalchamber 13 causes the salt water placed in chamber 13 to mix anddisperse throughout both chambers. Thus, the desired degree of salinityis achieved with respect to all the water in both the hatching andlarval chambers, automatically, by simply raising the water level.

Thus far nothing obstructs the larvae from swimming into the adjacentlarval chamber from the hatching chamber. At this point, a cover 25 isplaced over the hatching chamber 12 in which the hatch took place todarken it. Light sources 19, adjacent the larval chambers 13, are turnedon. This results in the larval chambers being brightly. illuminated withrespect to the hatching chambers. It is known that the larvae willmigrate toward a source of light, and they therefore swim from a chamber12 over bulkhead 15 into larval chamber 13. v

After some time, when the larval migration is complete, the screen meshdivider 18 is installed atop bulkhead 15. Screens 18 are of a gauge fineenough to prevent the larvae from returning to hatching tank 1 2.

It can be seen that, as soon as the larvae are completely hatched, thefemale s removal assumes that she will not pollute the environment andalso negates the possibility that she may devour her young.

Only one female can use the hatching tank at a given time, in which caseone chamber 12 would be empty and its adjacent larval tank not used. Asshould be apparent, two females can hatch larvae at the same time, onein each chamber 12. The larvae will then migrate to their respectiveadjacent larval chamber 13. [t is noted that walls 14 and 16 are solidand do not permit the passage of larvae from one hatching chamber toanother, nor from one larval chamber to another. The reason for this isthat larvae which are more than a few days old have both the capabilityand the inclination to devour newborn shrimp larvae. This is an earlymanifestation of the crustaceans cannibalistic tendency. Therefore,because female egg-bearing shrimp in adjacent hatching chambers mayhatch their young at different times, the young crustaceans must be keptin separate areas.

As has been noted above, it is critical in the early development ofshrimp larvae that, in order to get optimum growth and survival, waterconditions be closely controlled. The enormous numbers of shrimp larvaegenerate substantial quantities of waste material which must be removedat frequent intervals from the water. Water temperature must bemaintained within close limits. Waste food must be removed from thewater. The water may be changed frequently both to clean it and in orderthat there always be plenty of oxygen available to the growing larvae.To accomplish this, a suitable drain and filter system can be provided(not shown).

If the larvae were allowed to swim about at will through both thehatching and larval chambers, it would be extremely'difficult to operateupon, remove water from, or add water to the hatching tank withoutinjuring or pumping out larvae. By means of this invention, however, thelarvae are maintained in the volume of the larval chambers, leaving thehatching chamber empty of larvae. Therefore, pumps and hoses andstrainers and the like can be used to treat, remove from, or add waterto that which is present in the tank, without fear of either injuringlarvae or unwittingly pumping them away It is also noteworthy thatscreens 18, while being too fine to allow larvae to pass, do allow thecirculation of water from hatching chamber to larval chamber and back.This means that contamination of the water occurs at a slower rate thanit would if the only water available to the larval chamber were thatconfined within the walls of that chamber itself. Thus, this inventionenables the maintenance of greater stability in water conditions than ifthe larvae were simply confined in the larval chamber, with no watercirculation at all.

I It also has been found that larvae of various types of crustaceansexhibit a tendency to jump out of the water. The biological reason forthe jumping is not un- I derstood. The jumping commences at a time priorto metamorphosis and continues for some time after metamorphosis. In thecase of the species Macrobrachium Rosenbergi, jumping commences usuallywithin l5-20 days after the larvae have hatched and lasts for about aweek. The larvae jump from the water surface to the wall of the tank. Ifthe water level is close enough to the top of the hatching tank and/orthe larvae jump high enough, they clear the wall of the tank and fall onthe floor. These larvae are usually killed, thereby resulting in agreatly increased mortality rate for a given hatch. It has been foundthat the larvaecan be kept in the tank by washing down the tank wallswith water. By doing this, the mortality rate of any given hatch can bekept lower.

FIGS. 1 and2 show a spray pipe 40 which is located adjacent the fourwalls of each of the larval chambers 13. The spray pipe is connectedthrough a valve 42 to a source of water (not shown). The spray pipe,which can be of PVC plastic, has a number of holes along its lengthwhich are made so that the water from the pipe will flow onto thecorresponding adjacent wall of the tank. It is preferred that the spraypipe be located to form a water spray over. substantially the entirewall surface area. This prevents substantially all of the larvae fromjumping out of the tank. It is only necessary to supply water to thespray pipe 40 from a time just prior towhen they start to jump until atime after the jumping stops or until they are transferred to a growingtank.

FIG. 3 shows another form of larvae hatching tank according to theinvention. Here, a round tank 50 is provided which can be of anysuitable material such as metal, plastic or FIBERGLASS. It has beenfound that a round tank has certain advantages for hatching purposessince it can be made to provide a flowing action for the water which thelarvae seem to prefer.

A screen 52, which is closed on all sides and on the top, is located inthe center of tank 50 over a drain fitting 54. The drain fitting leadsto a filter system (not shown) so that the water in the tank can beconstantly recirculated and cleaned. The mesh size of the screen 52issuch to prevent larvae from being sucked into the drain 54. Lights 58are suspended above the surface of the water in the tank. As in the caseof FIG. 1, the lights aid in causing the hatched larvae to migrate tovarious parts of the tank. The tank also has the air supply pipe 29.

A spray pipe 58 is located around the upper rim of the tank. Pipe 58 isconnected to a source of fresh or filtered water through a valve 59. Thepipe is per forated to provide a water spray to wash down the walls ofthetank to prevent the larvae from jumping out of the tank, as explainedwith respect to FIGS. 1 and 2.

Larvae can be hatched in tank 50 in one of several ways. If desired, agravid female can be placed directly into the water of the tank andpermitted to hatch. The

water temperature and salinity are'adjust'ed and controlled as needed.

The female also can be placed in a container, such as a bucket, which ispartially filled with water. The container can be considered as formingthe hatching chamber. The female can be permitted to hatch the larvae inthe container either before or after it is placed in the water, of thetank. In the former case, when the container with female and larvae areplaced in the water of tank 50, the water circulation will cause thelarvae to be distributed throughout the tank. Migration of the larvae isaided by the lights58. Thefemale also can be permitted to hatch whilethe container is in the tank. In this case, the larvae also will migratethroughout the tank due to water circulation and the light stimulus. Thetop of the container can be covered, if desired,

with a large mesh screen to prevent the female from leaving while stillpermitting the larvae to migrate from the container after being hatched.After the hatch has been completed, the container, with the female, isremoved from the tank.

It should be evident herefrom that this invention is of substantialbenefit in the husbandry of very young crustacean life.

What is claimed is: v

l. A hatching tank for crustacea larvae comprising, means for drainingwater from said tank, means for preventing said larvae from beingdrained from the tank by said drain means, and means for supplying fluidto the tank wall above the normal level of water in the tank to preventthe larvae from jumping out of the tank.

2. A hatching tank as in claim 1, further comprising means for inducingthe larvae to migrate to various portions of the tank.

3. The hatching tank as in claim 1 furthercomprising means for isolatinga female, egg bearing crustacean within a predetermined portion of theoverall confines of said tank.

4. The hatching tank of claim 3 wherein said means for isolating thefemale crustacean comprises a container which can-be immersed into thefluid of said container while holding the female crustacean therein,said container having at least one opening to permit the larvae tomigrate therefrom into the fluid of the tank.

5. A hatching tank as in claim 4 further comprising means for inducingthe hatched larvae to'migrate from the container to various portions ofthe tank.

6. A hatching tank as in claim 1 wherein said tank is generallycircular, said fluid supply means comprising 'a ring located adjacentthe top of the tank and of the same general shape as the tank forsupplying the fluid to variousparts of the tank preventing the larvaefrom jumping out of the tank.

7. The method of providing a suitable environment for the hatching andearly development of crustacean larvae comprising the steps of:

hatching the crustacea larvae in a tank of water, and

discharging fluid onto the interior wall of the tank to prevent thecrustacea larvae from jumping out of the tank.

8. The method of claim 7 wherein said crustacea are hatched by placing afemale crustacean in the fluid within the confines of the tank.

water, said hatching chamber being in fluid com-' 10 to said hatchingchamber.

14. A tank for containing fluid to provide suitable environment forthehatching and early development of crustacealarvae, comprising:

a. means forming a hatching chamber,

b. means forming a larval chamber adjacent thereto,

c. means forming a passage way between the hatching and larval chambers,

d. inducing means to inducesaid larvae to migrate from said hatchingchamber to said larval chamber, and

e. fluid discharge means for supplying fluid to wash down the interiorof the walls of the larval chamber above the level of the fluidcontained .in said larval. I

15. The tank of claim 14 wherein said fluid supply means comprises meansfor surrounding a major portion of the tank wall defining the larvalchamber for supplying a plurality of streams of fluid to said wall.

1. A hatching tank for crustacea larvae comprising, means for draining water from said tank, means for preventing said larvae from being drained from the tank by said drain means, and means for supplying fluid to the tank wall above the normal level of water in the tank to prevent the larvae from jumping out of the tank.
 2. A hatching tank as in claim 1, further comprising means for inducing the larvae to migrate to various portions of the tank.
 3. The hatching tank as in claim 1 further comprising means for isolating a female, egg bearing crustacean within a predetermined portion of the overall confines of said tank.
 4. The hatching tank of claim 3 wherein said means for isolating the female crustacean comprises a container which can be immersed into the fluid of said container while holding the female crustacean therein, said container having at least one opening to permit the larvae to migrate therefrom into the fluid of the tank.
 5. A hatching tank as in claim 4 further comprising means for inducing the hatched larvae to migrate from the container to various portions of the tank.
 6. A hatching tank as in claim 1 wherein said tank is generally circulaR, said fluid supply means comprising a ring located adjacent the top of the tank and of the same general shape as the tank for supplying the fluid to various parts of the tank preventing the larvae from jumping out of the tank.
 7. The method of providing a suitable environment for the hatching and early development of crustacean larvae comprising the steps of: hatching the crustacea larvae in a tank of water, and discharging fluid onto the interior wall of the tank to prevent the crustacea larvae from jumping out of the tank.
 8. The method of claim 7 wherein said crustacea are hatched by placing a female crustacean in the fluid within the confines of the tank.
 9. The method of claim 7 wherein the step of placing the female crustacean in the tank comprises the step of placing the female in a container having at least one opening therein through which the larvae migrate to other portions of the tank.
 10. The method of claim 7 wherein the step of placing the female crustacean in the tank comprises: a. physically isolating a female crustacean bearing fertilized eggs in a hatching chamber containing water, said hatching chamber being in fluid communication with a larval chamber and b. inducing newly hatched larvae to migrate from said hatching chamber to said larval chamber.
 11. The method of claim 9 further comprising the step of inducing the larvae to migrate from the container to other portions of said tank.
 12. The method of claim 11 wherein said inducing step comprises illuminating said other portions of said tank.
 13. The method of claim 10 wherein said inducing step comprises illuminating said larval chamber relative to said hatching chamber.
 14. A tank for containing fluid to provide suitable environment for the hatching and early development of crustacea larvae, comprising: a. means forming a hatching chamber, b. means forming a larval chamber adjacent thereto, c. means forming a passage way between the hatching and larval chambers, d. inducing means to induce said larvae to migrate from said hatching chamber to said larval chamber, and e. fluid discharge means for supplying fluid to wash down the interior of the walls of the larval chamber above the level of the fluid contained in said larval.
 15. The tank of claim 14 wherein said fluid supply means comprises means for surrounding a major portion of the tank wall defining the larval chamber for supplying a plurality of streams of fluid to said wall. 